The present invention relates to photographic spectral sensitizing dyes and more particularly, to dyes useful as sensitizing dyes used for silver halide photographic light-sensitive materials.
Silver halide photographic light-sensitive materials are required to have high sensitivity in respectively different specific wavelength regions depending on their use. As one of techniques for such silver halide photographic light-sensitive materials, it has been well known to add various kinds of cyanine dyes and merocyanine dyes to silver halide photographic light-sensitive materials thereby to very effectively enhance the sensitivity in a specific wavelength region longer than the sensitive wavelength inherent to the silver halides.
When spectral sensitization with dyes is applied to silver halide photographic emulsions, not only the dyes must impart spectral sensitization effect and enhance the sensitivity, but also they must satisfy the following requirements.
(1) The spectral sensitization range is proper. PA1 (2) Stable photographic characteristics are maintained during storage of light-sensitive materials. PA1 (3) Stain or fog caused by residual dyes added for spectral sensitization is not left after development. PA1 (4) They have no unfavorable correlation with other photographic additives.
Considerably large number of sensitizing dyes have been known, but a few of them satisfy the above requirements such as sensitizability and photographic characteristics.